Contact tray for a mass transfer column

ABSTRACT

The valve cover has a guide vane extending laterally and downwardly from the central portion towards and in spaced relation to the tray deck for deflecting a majority of the vapor passing upwardly through an orifice downward towards the tray deck. A de-entrainment device with a downwardly angled deflector in vertical alignment with an orifice in the tray deck may be integrated or not with the valve cover below the tray deck.

This invention relates to a contact tray for a mass transfer column.More particularly, this invention relates to a valve cover for a contacttray for a mass transfer column. Still more particularly, this inventionrelates to a de-entrainment device for a contact tray for a masstransfer column.

As is known, various types of mass transfer columns have beenconstructed with contact trays that are arranged throughout the heightof the column in spaced apart relation with orifices disposed throughoutthe trays. In most cases, the trays are arranged so that a downcomingliquid can be directed across each tray and from tray-to-tray in azigzag manner over the height of the column via downcomers on one sideof each tray while an ascending vapor passes through the orifices sothat the liquid and vapor can enter into a mass transfer or heattransfer operation. In other cases, the trays have been made as circulardual flow trays so that vapor and liquid compete for travel through theorifices in each direction. In large columns with high liquid rates,multiple downcomers and multiple tray deck zones are used at each trayelevation.

In some cases, such as described in U.S. Pat. Nos. 3,463,464 and6,588,736, fluid deflector members are located directly above eachorifice in a tray deck in order to prevent the liquid from passingdownwardly though the vapor-introducing orifices formed in the trays. Asdescribed, the deflector members are formed out of the trays in anintegral manner. While a tray of this type is relatively strong due tothe integral construction of the deflector members within the tray deck,the lift heights of the deflector members, particularly in brittlematerials, has been limited. That is to say, since the formation of thedeflector members requires the material to stretch to a length greaterthan the depth of the material, the combination of significantelongation and brittle material can cause the deflector members to crackduring the forming process.

U.S. Pat. Nos. 5,911,922 and 5,762,834 describe bridge members that canbe mounted across the orifices of a contact tray and that function asmovable valves. These bridge members have required slots to be formed inthe contact tray adjacent to an orifice in order to mount the legs ofthe bridge members. As a result, the bridge members have been rathercumbersome to install.

U.S. Pat. No. 5,360,583 describes fluid deflector members that areintegral with a tray as well as a fluid deflector member that is movablewith respect to a tray and that has outturned feet to limit upwardmovement relative to a deck. However, such a construction is difficultto install.

U.S. Pat. No. 7,540,477 describes a tray valve for a tray column that isof relatively simple construction.

SU 1369740 describes a mist eliminator that relies on a series ofcoupled two-deck devices.

Mass transfer columns have also been constructed with contact trays thatcooperate with de-entrainment devices to collect entrainment, i.e.liquid carried with the vapor upwardly from a tray deck opposite to theintended direction, before the entrainment reaches the tray deck aboveand distributes the entrainment back to the tray deck below.

Accordingly, it is an object of the invention to provide a valve coverfor a contact tray of relatively simple construction. It is anotherobject of the invention to increase the capacity of the tray containingvalve covers. It is another object of the invention to improve theentrainment resistance of a tray in a tray column. It is another objectof the invention to provide a valve cover that can be easily mounted ona tray. It is another object of the invention to provide a valve cover,that can fixedly mounted on a tray deck or allowed to move up and downrelative to a tray deck.

Briefly, the invention provides a contact tray for a mass transfercolumn comprised of a tray deck having a plurality of orifices forpassage of an ascending vapor therethrough and a plurality of valvecovers positioned over the orifices to control the passage of vapor.

Typically, a plurality of horizontal tray decks are disposed in spacedvertical relation within a tower and means are provided for directing aflow of liquid laterally across each tray deck in a sequential mannerfrom top to bottom of the tower.

In an embodiment each said valve cover is mounted over a respective oneof said orifices and having a central portion disposed in spacedrelation to said tray deck and over a respective orifice and at leastone guide vane extending laterally and downwardly from said centralportion towards said tray deck for deflecting at least a part of thevapor ascending through a respective orifice towards said tray deck.

A least some of said valve covers can have a pair of legs extending fromopposite ends of said central portion onto said tray deck and a pair ofpanels, each said panel extending between a respective one of said pairof legs and said guide vane for deflecting a part of the vapor ascendingthrough a respective orifice towards said tray deck. Furthermore eachsaid valve cover can have means for engaging said tray deck to preventlifting of said respective valve cover from said tray deck. Said meanscan include a deformable tab extending from at least one of said legsthrough a slot in said tray deck to abut an underside of said tray deck.

In an embodiment each said valve cover can have means for engaging saidtray deck to allow lifting of said respective valve cover from said traydeck a predetermined amount.

Said means may include a pair of extensions, each said extensionextending from a respective leg of said pair of legs, each saidextension including a first portion for passing through said orifice ofsaid deck, a second portion extending downwardly from said first portionand towards a second portion of the other of said pair of extensions anda U-shaped portion extending upwardly from said second portion anddefining a pair of prongs spaced from said tray deck a predetermineddistance for abutting an underside of said tray deck in response tolifting of said valve cover relative to said tray deck.

A contact tray according to any one of the embodiments can furthercomprise an opening in a selected one of said central portion and saidlegs for passage of vapor therethrough. Furthermore each said valvecover can have a pair of said guide vanes extending laterally anddownwardly from opposite sides of said central portion towards said trayfor deflecting at least a part of the vapor ascending through arespective orifice towards said tray. In addition or as an alternativeeach said valve cover can have a plurality of panels, each said panelcan extend between a respective one of said pair of legs and arespective one of said guide vanes for deflecting a part of the vaporascending through a respective orifice towards said tray deck.

A contact tray according to any one of the embodiments can furthercomprise a plurality of de-entrainment devices, each said de-entrainmentdevice can extend from a respective valve cover below said tray deck andcan include a deflector in vertical alignment with a respective orificein said tray deck. Furthermore said deflector can be downwardly angledand can include a pair of longitudinally extending blades disposed inangular relation to each other. In addition thereto or alternativelysaid deflector can be horizontally disposed and can include a pluralityof slots and at least one downwardly inclined finger within each slot.

Furthermore each de-entrainment device can have a vertically disposedleg connecting said deflector to a respective valve cover.

A contact tray according to any one of the embodiments can be furtherconfigured such that each said orifice in said tray deck has a centralsection and at least a pair of end sections of smaller width than saidcentral section extending from opposite ends of said central section andeach said valve cover can have a pair of sloped legs at opposite ends,each said leg of each said valve cover extending into a respective endsection of a respective orifice.

The tray deck of a contact tray according to any one of the embodimentscan include at least one slot adjacent a respective orifice and eachsaid valve cover can have a leg extending from said central portion intosaid slot.

A valve cover for a mass transfer column according to the inventioncomprises a central portion for disposition in spaced relation to anorifice for passage of an ascending flow of vapor in a tray deck; a pairof legs extending downwardly from opposite ends of said central portion;and at least one guide vane extending laterally and downwardly from saidcentral portion for deflecting at least a part of the vapor ascendingthrough a respective orifice towards said tray deck.

The valve cover can further comprise a pair of panels, each said panelextending between a respective one of said pair of legs and said guidevane for deflecting a part of the vapor ascending through a respectiveorifice towards the tray deck.

Alternatively or in addition thereto each valve cover can comprise afirst opening in said central portion and a second opening in one ofsaid legs. The valve cover can further comprise a deformable tabextending from at least one of said legs for passage through a slot in atray deck for abutting an underside of the tray deck upon deformationthereof.

The valve cover can further comprise a pair of depending extensions,each said extension including a first portion for passing through saidorifice of said deck, a second portion extending downwardly from saidfirst portion and towards a second portion of the other of said pair ofextensions and a U-shaped portion extending upwardly from said secondportion and defining a pair of prongs spaced from said tray deck apredetermined distance for abutting an underside of said tray deck inresponse to lifting of said valve cover relative to said tray deck.

In addition, each said U-shaped portion can be directed upwardly in adirection away from the U-shaped portion of the other of said pair ofextensions.

In an embodiment, a valve cover can further comprise a pair of saidguide vanes extending laterally and downwardly from opposite sides ofsaid central portion and a plurality of panels, each said panel canextend between a respective one of said pair of legs and a respectiveone of said guide vanes for deflecting a part of the vapor ascendingthrough a respective orifice towards the tray deck.

In an embodiment, a valve cover can further comprise a de-entrainmentdevice extending downwardly from one of said legs. The de-entrainmentdevice can have a downwardly angled deflector in vertical alignment saidcentral portion. The deflector can include a pair of longitudinallyextending blades disposed in angular relation to each other.Furthermore, the de-entrainment device can have a vertically disposedleg connecting said deflector to one of said legs.

In an embodiment, a de-entrainment device for a mass transfer columncomprises a downwardly angled deflector for positioning in verticalalignment below an orifice in a tray deck, said deflector having atleast longitudinally extending blade disposed in angular relation to ahorizontal plane and a vertical plane; and at least one verticallydisposed leg extending from said deflector for mounting of saiddeflector below a tray deck. Said deflector can include a pair of saidblades disposed in angular relation to each other.

In an embodiment, a de-entrainment device for a mass transfer columncomprises a horizontally disposed deflector for positioning in verticalalignment below an orifice in a tray deck, said deflector beingfenestrated with a series of bars separated by slots and downwardlyinclined fingers in alignment with said slots; and at least onevertically disposed leg extending from said deflector for mounting ofsaid deflector below a tray deck. Said fingers can be disposed in tworows with said fingers on one row being oppositely disposed to saidfingers of the other of said two rows.

In an embodiment, the invention further comprises a combinationincluding a tower disposed on a vertical axis; and a plurality ofhorizontal tray decks disposed in spaced vertical relation within saidtower for receiving flows of liquid thereon, each said tray deck havinga plurality of orifices for passage of an ascending vapor therethrough;and a plurality of valve covers mounted on each respective tray deck,each said valve cover having a central portion disposed in spacedrelation to a respective orifice in a respective tray deck and at leastone guide vane extending laterally and downwardly from said centralportion towards and in spaced relation to said respective tray deck fordeflecting at least a part of the vapor ascending through a respectiveorifice towards said respective tray deck.

The combination can further comprise a plurality of de-entrainmentdevices, each said de-entrainment device extending from a respectivevalve cover below a respective tray deck and having a deflector invertical alignment with a respective orifice in said respective traydeck. Alternatively or in addition thereto each de-entrainment devicecan have a vertically disposed leg connecting said deflector to one ofsaid legs of a respective valve cover.

Each valve cover is mounted on the tray deck and may be of any suitableshape, such as, a multi-chordal shape or a semi-circular shape. Forexample, one preferred shape is a valve cover that has a central portiondisposed in spaced relation to the tray deck and over a respectiveorifice and a pair of legs extending from opposite ends of the centralportion onto the tray deck.

In accordance with the invention, each valve cover has at least oneguide vane extending laterally and downwardly from the central portiontowards the tray deck for deflecting at least a part of the vaporascending through a respective orifice towards the tray deck. Theseguide vanes direct the vapor flow more laterally and into the liquid onthe tray deck and were found to unexpectedly produce a significantincrease in capacity of the tray containing these valves.

Each valve body may be made of solid construction, i.e. without holes,or with one or more holes, for example, with an opening in the centralportion and/or an opening in the leg in the front of the valve cover.

In one embodiment, the valve cover and tray deck orifices areconstructed as described in U.S. 2009/0134533, the disclosure of whichis incorporated herein, and the valve covers are provided with a guidevane on each lateral side of the central portion that extends laterallyand downwardly towards the tray deck for deflecting at least a part ofthe vapor ascending through a respective orifice towards the tray deck.

In another embodiment, the valve cover is provided with means forengaging the tray deck to prevent lifting of the valve cover from thetray deck. For example, this means may be a deformable tab that extendsfrom at least one of the sloped portions through a slot in the tray deckto abut an underside of the tray deck when deformed as by being twisted.

The valve cover may also be provided with means for engaging the traydeck to allow lifting, i.e. an up and down movement, of the valve coverfrom the tray deck a predetermined amount. This means may be anextension that extends from each leg and includes a first portion thatextends through the orifice in the deck, a second portion that extendsdownwardly from the first portion and towards a second portion anddefining a pair of prongs spaced from the tray deck a predetermineddistance for abutting an underside of the tray deck in response tolifting of the valve cover relative to the tray deck.

In another embodiment, the valve covers are provided with panels betweenthe guide vanes and the adjacent leg of the cover to provide for a moreuniform flow of vapor from the sides of the valve cover and downwardlyonto the tray deck.

The invention also provides a de-entrainment device having a downwardlyangled deflector for positioning in vertical alignment below an orificein the tray deck to collect entrainment before the entrainment reachesthe tray deck and distributes the entrainment back to the tray deckbelow.

In one embodiment, the deflector may be formed from the orifice in thetray deck.

In another embodiment, the deflector may be formed of a pair oflongitudinally extending blades that are disposed in angular relation toeach other. The sloping of the blades is such that liquid drains towardsthe outlet of the tray deck below thereby helping to transport theliquid forward on that tray deck. In this embodiment, the deflector mayhave a vertically disposed leg connecting the deflector to one of thelegs of a valve cover to form a one-piece structure.

Such a one-piece structure may be readily mounted in an orifice of thetray deck by passing the deflector first through the orifice and thenturning the structure to position the valve cover over the orifice.Where the one-piece structure has a valve cover as described in U.S.2009/0134533, the sloped legs of the valve cover from which thedeflector extends may be positioned within an end section of theorifice. Where the one-piece structure has a valve cover with adeformable tab at the end of a leg, the tab may be passed through a slotprovided therefor in the tray deck. Thereafter, the deformable tab maybe twisted to secure the one-piece structure to the tray deck. In thiscase, only the one leg of the valve cover has a deformable tab.

In another embodiment, the deflector may have a pair of verticallydisposed legs extending from the deflector for mounting of the deflectordirectly to the tray deck.

These and other objects and advantages of the invention will become moreapparent from the following detail and description, taken in conjunctionwith the accompanying drawings wherein:

FIG. 1 illustrates a perspective view of a section of a tray deck with avalve cover in accordance with the invention;

FIG. 2 illustrates a view taken on line 2-2 of FIG. 1;

FIG. 3 illustrates a part perspective view of a modified contact tray inaccordance with the invention;

FIG. 4 illustrates a bottom view of the contact tray of FIG. 3;

FIG. 5 illustrates an exploded view of a valve cover and tray deck witha schematic indication of the directions of flow of vapor from the valvecover;

FIG. 6 is a simulation of a vapor flow pattern through a valve cover inaccordance with the invention;

FIG. 7 illustrates a perspective view of a valve cover and integratedde-entrainment device in accordance with the invention;

FIG. 8 illustrates a perspective view of a modified valve cover inaccordance with the invention;

FIG. 9 illustrates a perspective view of the valve cover of FIG. 8 withan integrated de-entrainment device in accordance with the invention;

FIG. 10 illustrates a perspective view of a modified de-entrainmentdevice in accordance with the invention;

FIG. 11 illustrates a schematic view of a tower employing a series ofvertically disposed contact trays in accordance with the invention;

FIG. 12 illustrates a perspective view of a modified valve cover withpanels on a tray deck in accordance with the invention;

FIG. 13 illustrates a perspective view similar to FIG. 12 of a modifiedvalve cover with larger panels in accordance with the invention;

FIG. 14 illustrates a perspective exploded view of a valve cover andtray wherein the valve cover is mounted on the tray to be movable up anddown in accordance with the invention; and

FIG. 15 illustrates a side view of the valve cover of FIG. 14 in placeon the tray deck of FIG. 14.

Referring to FIG. 11, the tower 10 is disposed on a vertical axis and isconstructed in a conventional manner. As indicated, the tower 10contains a plurality of horizontally disposed contact trays 11 that aredisposed over the height of the column 10 in spaced vertical relation toeach other and a plurality of downcomers 12. The downcomers 12 areconstructed in a conventional fashion to communicate one side of arespective contact tray 11 with an opposite side of the contact tray 11immediately below in order to direct a flow of liquid 13 horizontallyacross the respective contact trays in a zigzag manner. In some cases,there may be more than one downcomer per tray 11.

Referring to FIGS. 1 and 2, each contact tray 11 has a tray deck 14 thathas a plurality of orifices 15 for passage of an ascending vaportherethrough for mass transfer or heat transfer with the liquid as wellas a plurality of valve covers 16 for preventing the liquid from passingthrough the orifices 15 and to direct the flow of vapor laterally of theorifices 15.

Each orifice 15 is shaped as described in U.S. 2009/0134533 with acentral section 17 and a pair of rectangular end sections 18 of smallerwidth that extend from opposite ends of the central section 17.

Each valve cover 16 is mounted over a respective orifice 15 and has acentral portion 19 disposed in spaced relation to the tray deck 14 andover a respective orifice 15 and a pair of legs 20 that extend fromopposite ends of the central portion 19 in a sloped manner onto the traydeck 14. Each leg 20 has a reduced end section forming a tab 21 thatfits into an end section 18 of an orifice 15.

The central section 17 of an orifice 15 is of trapezoidal shape. In thiscase, one leg 20 of the valve cover 16 is narrower than the other leg 20and positioned on the downstream side of the orifice 15 relative to theliquid flow F (see FIG. 1). Therefore, the vapor leaving the valve cover16 has a slight pushing component that helps the liquid move across thetray deck 14. This appears to help in capacity and maybe efficiency toforce a plug flow of liquid across the deck 14.

Referring to FIGS. 1 and 2, each valve cover 16 is provided with one ormore guide vanes 22 on the side of the central portion 19 that extendlaterally and downwardly from the central portion 19 towards and inspaced relation to the tray deck 14 for deflecting at least a part ofthe vapor ascending through a respective orifice 15 towards the traydeck 14, as indicated by the arrows 28 in FIG. 5 and the simulation ofFIG. 6.

Referring to FIG. 3, wherein like reference characters indicate likeparts as above, the tray deck 14 may be made with orifices 15 oftrapezoidal or rectangular shape with slots 25 disposed adjacent twoends and each valve cover 16′ has a central portion 19, a pair of legs20 at opposite ends of the central portion 19 that slope towards thetray deck 14 and a pair of tabs 21, each of which extends verticallyfrom the end of a sloped leg 20 to pass through a slot 25 in the traydeck 14 adjacent the orifice 15.

As indicated in FIG. 4, each orifice 15 is of trapezoidal shape. In thiscase, as above, leg 20 of the valve cover 16′ is narrower that the otherleg 20 and positioned on the downstream side of the orifice 15 relativeto the direction of liquid flow F. Therefore, the vapor leaving thevalve cover 16′ has a slight pushing component that helps the liquidmove across the tray deck 14.

Alternatively, each orifice 15 may be of rectangular shape with the sizebeing the equivalent of a circular orifice of about 15 mm to 20 mm.

Referring to FIG. 4, each valve cover 16′ also has means, for example,in the form of a deformable T-shaped tab 21′ extending from a leg 20,for engaging the underside of the tray deck 14 to prevent lifting of thevalve cover 16′ from the tray deck 14. In this embodiment, thedeformable tab 21′ is twisted to engage the underside of the tray deck14.

As shown in FIGS. 3 and 4, each valve cover 16′ has an opening 26 in thecentral portion 19 and an opening 27 in the sloped leg 20 in the front(downstream side) of the valve cover 16′. Alternatively, the valve cover16′ may be made without holes, i.e. of solid construction, as indicatedin FIGS. 5 and 6.

Referring to FIGS. 1 to 4, each valve cover 16, 16′ is provided with oneor more guide vanes 22 on the side of the central portion 19 that extendlaterally and downwardly from the central portion 19 towards and inspaced relation to the tray deck 14 for deflecting at least a part ofthe vapor ascending through a respective orifice 15 towards the traydeck 14, as indicated by the arrows 28 in FIG. 5 and the simulation ofFIG. 6.

As indicated in FIG. 6, the guide vanes 22 are constructed to direct amajority of the vapor passing upwardly through an orifice 15 downwardtowards the tray deck 14. To this end, the width of each guide vane 22is a major fraction of the width of the central portion 19 and about ⅓the width of an orifice 15, for example, the width of a guide vane 22 is15 mm.

In addition, each guide vane 22 is spaced from the tray deck 14 by adistance in a range of from 3 mm to 10 mm with a preferred range of from3 to 5 mm.

Experimental results have shown that by redirecting the vapor flow fromthe valve cover 16, a substantial improvement in capacity can beachieved. Specifically, an improvement of approximately 15% can be seenwith the configuration of tray deck 14 and valve covers 16 of FIG. 1.

As indicated in FIG. 5, wherein like reference characters indicate likeparts as above, each guide vane 22 slopes uniformly towards the traydeck 14 and has a free edge parallel to and spaced from the tray deck14. The deflected vapor thus exits from under the guide vane 22 in adirection as indicated by the arrow 28 transverse, i.e. perpendicular,to the flow of liquid on the tray deck 14 which is from left to right inFIG. 2.

In another embodiment, the guide vane 22 may be folded in such a way asto direct the vapor exiting from under the guide vane in a directionforwardly so that the exiting vapor moves in the direction of liquidflow. For example, the guide vane may extend laterally outwardly fromthe central portion 19 of the valve cover 16 and the end portion of theguide vane may be folded or bent downwardly about a fold line angularlydisposed across the guide vane. In such a case, the depending endportion would have a greater length on one side than at the other sideand would be spaced from the tray deck 14 a smaller amount on the oneside than on the other side. Alternatively, the depending end portionmay be made so as to be equi-spaced from the tray deck 14 along thewidth thereof while providing a deflecting wall for deflecting the vaporforwardly along the tray deck 14.

The guide vanes 22 may be employed on any suitable valve coverincluding, but not limited to the embodiments of valve covers describedin U.S. 2009/0134533.

Further, a de-entrainment device may be employed with any of theabove-mentioned valve covers. For example, referring to FIG. 7, eachvalve cover 16′ may be integrated with a de-entrainment device 29 into aone-piece structure. As illustrated, the de-entrainment device 29extends downwardly from one of the sloped legs 20 and includes avertically disposed leg 30 integral with the dependent tab 21 of the leg20 that extends through the tray deck 14. In this case, the tab 21 isnot deformable. The de-entrainment device 29 may also be fabricated soas to extend downwardly from both of the sloped legs 20.

The de-entrainment device 29 also has a downwardly angled deflector 31integral with the bottom of the leg 30 that is disposed in verticalalignment with an orifice 15 in the tray deck 14 and the central portion19 of the valve cover 16′. The deflector 31 is positioned to collectentrainment before the entrainment reaches the tray deck 14 above anddistributes the entrainment back to the tray deck 14 below (not shown).

In the illustrated embodiment, the deflector 31 is formed of a pair oflongitudinally extending blades 32 that are disposed in angular relationto each other. Alternatively, the deflector may be formed of a singleblade 32 that is disposed at an angle to a horizontal plane and an angleto a vertical plane, e.g. by eliminating one of the blades 32 of thedeflector 31.

The integrated structure of valve cover 16′ and de-entrainment device 29may be readily mounted in an orifice 15 of the tray deck 14 by passingthe deflector 31 first through the orifice 15 and then turning thestructure to position the valve cover 16′ over the orifice 15. Thedeformable tab 21 of the valve cover 16′ is the passed through the slot25 provided therefor in the tray deck 14 and twisted to secure thestructure to the tray deck 14.

Referring to FIGS. 8 and 9, wherein like reference characters indicatelike parts as above, in another embodiment, the valve cover 16″ may beconstructed of a central portion 19 and a pair of legs 20 having asloped portion extending from the central portion 19 and a tab 33 thatextends perpendicularly from the sloped portion to pass through the traydeck 14. In order to prevent the valve cover 16″ from being blown awayfrom the tray deck 14, each tab 33 is provided with an outwardlyextending barb 34 for engaging under the tray 11 when in place. In thisembodiment, a de-entrainment device 29 extends downwardly from a tab 33and below the orifice.

Referring to FIG. 9, in this embodiment, the tab 33 may be elongated toform the vertical leg 30 of the de-entrainment device 29 or may beseparately joined to the vertical leg 30 of the de-entrainment device29.

Referring to FIG. 10, the de-entrainment device 29′ may be made with ahorizontally disposed deflector 31′ of rectangular shape that isfenestrated to have a series of bars 35 separated by slots 36 and pairsof downwardly inclined fingers 37 within each slot 36 and disposed inopposition to each other. As indicated, the fingers 37 are cut out ofthe deflector 31′ to form the slots 36. In this embodiment, thehorizontally disposed deflector 31′ is aligned vertically below anorifice 15 in the tray deck 14 to shadow the orifice 15 and entrainmentcollects on the surfaces of the deflector 31′ and travels along and downthe respective fingers 37 to descend onto the tray below.

As shown in FIG. 10, a pair of fingers 37 is cut from deflector 31′ toform a single slot 36 with the fingers 37 disposed in oppositedirections relative to each other. As shown, the fingers 37 are disposedin two rows with the fingers 37 on one row being oppositely disposed tothe fingers 37 of the other of the two rows. Alternatively, the fingersmay be directed in the same direction. In this latter embodiment, eachfinger would form a single slot.

As above described, the horizontally disposed deflector 31′ may extendfrom a single vertically disposed leg that is integrated with a tab 21on a leg 20 of a valve cover 16 or, as illustrated, may be suspended bya pair of integral legs 38 from a tray deck 14 above.

The vane-containing valve covers 16 when combined with thede-entrainment devices 29 have been found to achieve an 18% improvementin capacity in air/water showing that the benefits of both these valvemodifications are essentially cumulative.

Referring to FIG. 12, wherein like reference characters indicate likeparts as above, the valve cover 16 is provided with a plurality ofpanels 39, each of which extends between a respective leg 20 and arespective guide vane 22 for deflecting a part of the vapor ascendingthrough an orifice 15 towards the tray deck 14. By closing off theotherwise open corners between the guide vane 22 and the legs 20, a moreuniform vapor flow out of the valve cover 16 should be achieved alongwith directing of the vapor downward to the tray deck 14.

As indicated in FIG. 12, each panel 39 is of triangular shape andextends over the height of the guide vane 22, i.e. the extent of theguide 22 from the central portion 19, and over one-half the height of aleg 20, i.e. the extent of the leg 20 from the central portion 19 to thesurface of the tray deck 14.

Alternatively, as indicated in FIG. 13, wherein like referencecharacters indicate like parts as above, each panel 39′ is of triangularshape and greater extent than the panel 39 of FIG. 12. That is, eachpanel 39′ extends over the height of the guide vane 22, i.e. the extentof the guide 22 from the central portion 19, and substantially over theheight of a leg 20, i.e. the extent of the leg 20 from the centralportion 19 to the surface of the tray deck 14, leaving a small gap 40.

Referring to FIGS. 14 and 15, wherein like reference characters indicatelike parts as above, the valve cover 16 is constructed in a mannersimilar to the valve cover 16 of FIG. 13 and is provided with means forengaging the tray deck 14 to allow lifting, i.e. an up and downmovement, of the valve cover 16 from the tray deck 14 a predeterminedamount. As illustrated, this means includes a pair of dependingextensions 41 that extend from the legs 20 for passing through anorifice 15 in the tray deck 14.

As indicated in FIG. 15, each extension 41 has a first portion 43 thatpasses through the tray deck 14 and that is perpendicular to the traydeck 14, a narrower second portion 44 that extends downwardly from thefirst portion 43, through the orifice 15 and angularly towards thesecond portion of the other extension 41 and a U-shaped portion 45 thatextends upwardly from the second portion 44.

As illustrated, the first portion 43 of each extension 41 is sized topass through the tray deck 14 while the guide vanes 22 seat on the traydeck 14. As shown, each portion 43 is of rectangular shape.

The second portion 44 of each extension 41 is of rectangular shape andextends inwardly under the tray deck 14 so as to form a “diamond” shapewith the valve cover 16. This configuration of the extensions 41prevents the valve cover 16 from lifting out of the tray deck 14 afterbeing installed.

The U-shaped third portion 45 of each extension 41 extends upwardly at adifferent angle from the second portion 44, e.g. in a direction awayfrom the U-shaped portion 45 of the other extension 41. Each U-shapedportion 45 is of a width to pass through the orifice 15 and defines apair of prongs 46 for abutting an underside of the tray deck 14 inresponse to lifting of the valve cover 16 relative to the tray deck 14.

As shown in FIG. 14, a small transition section 47 is disposed betweenthe two portions 44, 45 to facilitate bending of the U-shaped portion ata different angle from the second portion 44. Referring to FIG. 14, inorder to install the valve cover 16, the lower ends of the U-shapedportions 45 are passed through the orifice 15 in the tray deck 14. Asthe extensions 41 pass through the orifice, the prongs 46 flex inwardlytowards each other. After passing the U-shaped portions 45 through theorifice 15, the prongs 46 are allowed to flex back to the original shapethereby forming a stop to prevent lifting of the valve cover 16 out ofthe tray deck 14. Once the valve cover 16 is in place, the guide vanes22 of the valve cover 16 are seated on the tray deck 14 and the prongs46 are spaced from the underside of the tray deck 14.

During operation of a tower, an upward flow of vapor through the orifice15 lifts the valve cover 16 from the tray deck 14 until such time as theprongs 46 come into contact with the underside of the tray deck 14thereby limiting the lift of the valve cover 16. During this time, thefirst portions 43 of the two extensions 41 are guided within the orifice15 so as to prevent lateral movement of the valve cover 16″.

Alternatively the first portion 43 of each extension 41 may be made of anarrower width than the leg 20 from which the portion 43 depends so asto be guided within a notch (not shown) that is formed in the tray deck14 as an adjunct to the rectangular orifice 15 in order to preventlateral movement of the valve cover 16″ during lifting of the valvecover 16″. Alternatively, the first portion 43 of each extension 41 maybe sized to seat on the top of the tray deck 14 while the second portion44 is guided in a notch (not shown) adjoining the orifice 15 in order toprevent lateral movement of the valve cover 16″ during lifting of thevalve cover 16″.

The invention thus provides a valve cover for a contact tray ofrelatively simple construction and one which increases the capacity ofthe tray.

The invention further provides a de-entrainment device that improves theentrainment resistance of a contact tray in a tray column.

1. A contact tray for a mass transfer column comprising a tray deck forreceiving a flow of liquid thereon, said tray deck having a plurality oforifices for passage of an ascending vapor therethrough; and a pluralityof valve covers, each said valve cover being mounted over a respectiveone of said orifices and having a central portion disposed in spacedrelation to said tray deck and over a respective orifice and at leastone guide vane extending laterally and downwardly from said centralportion towards said tray deck for deflecting at least a part of thevapor ascending through a respective orifice towards said tray deck. 2.A contact tray as set forth in claim 1 wherein at least some of saidvalve covers have a pair of legs extending from opposite ends of saidcentral portion onto said tray deck and a pair of panels, each saidpanel extending between a respective one of said pair of legs and saidguide vane for deflecting a part of the vapor ascending through arespective orifice towards said tray deck.
 3. A contact tray as setforth in claim 2 wherein each said valve cover has means for engagingsaid tray deck to prevent lifting of said respective valve cover fromsaid tray deck.
 4. A contact tray as set forth in claim 3 wherein saidmeans includes a deformable tab extending from at least one of said legsthrough a slot in said tray deck to abut an underside of said tray deck.5. A contact tray as set forth in claim 2 wherein each said valve coverhas means for engaging said tray deck to allow lifting of saidrespective valve cover from said tray deck a predetermined amount.
 6. Acontact tray as set forth in claim 5 wherein said means includes a pairof extensions, each said extension extending from a respective leg ofsaid pair of legs, each said extension including a first portion forpassing through said orifice of said deck, a second portion extendingdownwardly from said first portion and towards a second portion of theother of said pair of extensions and a U-shaped portion extendingupwardly from said second portion and defining a pair of prongs spacedfrom said tray deck a predetermined distance for abutting an undersideof said tray deck in response to lifting of said valve cover relative tosaid tray deck.
 7. A contact tray as set forth in claim 1, furthercomprising an opening in a selected one of said central portion and saidlegs for passage of vapor therethrough.
 8. A contact tray as set forthin claim 1 wherein each said valve cover has a pair of said guide vanesextending laterally and downwardly from opposite sides of said centralportion towards said tray for deflecting at least a part of the vaporascending through a respective orifice towards said tray.
 9. A contacttray as set forth in claim 8 wherein each said valve cover has aplurality of panels, each said panel extending between a respective oneof said pair of legs and a respective one of said guide vanes fordeflecting a part of the vapor ascending through a respective orificetowards said tray deck.
 10. A contact tray as set forth in claim 1further comprising a plurality of de-entrainment devices, each saidde-entrainment device extending from a respective valve cover below saidtray deck and having a deflector in vertical alignment with a respectiveorifice in said tray deck.
 11. A contact tray as set forth in claim 10wherein said deflector is downwardly angled and includes a pair oflongitudinally extending blades disposed in angular relation to eachother.
 12. A contact tray as set forth in claim 10 wherein saiddeflector is horizontally disposed and includes a plurality of slots andat least one downwardly inclined finger within each slot.
 13. A contacttray as set forth in claim 8 wherein each de-entrainment device furtherhas a vertically disposed leg connecting said deflector to a respectivevalve cover.
 14. A contact tray as set forth in claim 1 wherein eachsaid orifice in said tray deck has a central section and at least a pairof end sections of smaller width than said central section extendingfrom opposite ends of said central section and each said valve cover hasa pair of sloped legs at opposite ends, each said leg of each said valvecover extending into a respective end section of a respective orifice.15. A contact tray as set forth in claim 1 wherein said tray deckincludes at least one slot adjacent a respective orifice and each saidvalve cover has a leg extending from said central portion into saidslot.
 16. A valve cover for a mass transfer column comprising a centralportion for disposition in spaced relation to an orifice for passage ofan ascending flow of vapor in a tray deck; a pair of legs extendingdownwardly from opposite ends of said central portion; and at least oneguide vane extending laterally and downwardly from said central portionfor deflecting at least a part of the vapor ascending through arespective orifice towards said tray deck.
 17. A valve cover as setforth in claim 16 further comprising a pair of panels, each said panelextending between a respective one of said pair of legs and said guidevane for deflecting a part of the vapor ascending through a respectiveorifice towards the tray deck.
 18. A valve cover as set forth in claim16 further comprising a first opening in said central portion and asecond opening in one of said legs.
 19. A valve cover as set forth inclaim 16 further comprising a deformable tab extending from at least oneof said legs for passage through a slot in a tray deck for abutting anunderside of the tray deck upon deformation thereof.
 20. A valve coveras set forth in claim 16 further comprising a pair of dependingextensions, each said extension including a first portion for passingthrough said orifice of said deck, a second portion extending downwardlyfrom said first portion and towards a second portion of the other ofsaid pair of extensions and a U-shaped portion extending upwardly fromsaid second portion and defining a pair of prongs spaced from said traydeck a predetermined distance for abutting an underside of said traydeck in response to lifting of said valve cover relative to said traydeck.
 21. A valve cover as set forth in claim 20 wherein each saidU-shaped portion is directed upwardly in a direction away from theU-shaped portion of the other of said pair of extensions.
 22. A valvecover as set forth in claim 16 further comprising a pair of said guidevanes extending laterally and downwardly from opposite sides of saidcentral portion and a plurality of panels, each said panel extendingbetween a respective one of said pair of legs and a respective one ofsaid guide vanes for deflecting a part of the vapor ascending through arespective orifice towards the tray deck.
 23. A valve cover as set forthin claim 16 further comprising a de-entrainment device extendingdownwardly from one of said legs.
 24. A valve cover as set forth inclaim 23 wherein said de-entrainment device has a downwardly angleddeflector in vertical alignment said central portion.
 25. A valve coveras set forth in claim 24 wherein said deflector includes a pair oflongitudinally extending blades disposed in angular relation to eachother.
 26. A valve cover as set forth in claim 24 wherein saidde-entrainment device has a vertically disposed leg connecting saiddeflector to one of said legs.
 27. A de-entrainment device for a masstransfer column comprising a downwardly angled deflector for positioningin vertical alignment below an orifice in a tray deck, said deflectorhaving at least longitudinally extending blade disposed in angularrelation to a horizontal plane and a vertical plane; and at least onevertically disposed leg extending from said deflector for mounting ofsaid deflector below a tray deck.
 28. A de-entrainment device as setforth in claim 27 wherein said deflector has a pair of said bladesdisposed in angular relation to each other.
 29. A de-entrainment devicefor a mass transfer column comprising a horizontally disposed deflectorfor positioning in vertical alignment below an orifice in a tray deck,said deflector being fenestrated with a series of bars separated byslots and downwardly inclined fingers in alignment with said slots; andat least one vertically disposed leg extending from said deflector formounting of said deflector below a tray deck.
 30. A de-entrainmentdevice set forth in claim 29 wherein said fingers are disposed in tworows with said fingers on one row being oppositely disposed to saidfingers of the other of said two rows.
 31. In combination, a towerdisposed on a vertical axis; and a plurality of horizontal tray decksdisposed in spaced vertical relation within said tower for receivingflows of liquid thereon, each said tray deck having a plurality oforifices for passage of an ascending vapor therethrough; and a pluralityof valve covers mounted on each respective tray deck, each said valvecover having a central portion disposed in spaced relation to arespective orifice in a respective tray deck and at least one guide vaneextending laterally and downwardly from said central portion towards andin spaced relation to said respective tray deck for deflecting at leasta part of the vapor ascending through a respective orifice towards saidrespective tray deck.
 32. The combination as set forth in claim 31further comprising a plurality of de-entrainment devices, each saidde-entrainment device extending from a respective valve cover below arespective tray deck and having a deflector in vertical alignment with arespective orifice in said respective tray deck.
 33. The combination asset forth in claim 32 wherein each de-entrainment device has avertically disposed leg connecting said deflector to one of said legs ofa respective valve cover.